Of the many processes used in construction for measuring, scoring and marking parallel lines the number of means applied will depend on materials and circumstances. These tasks and other building methods can be made easier, simpler and quicker by modifying the tape measure to improve its ability to be used in other manners for different applications.
Carpenters needing to cut a piece of plywood to a consistent parallel width will often use a measuring tape with a chalk line to make a visual reference for guiding a saw. This process involves making measurements using a pencil to mark an indicator at either end of the sheet of plywood. The tape is set aside and a chalk line is then secured to the indicator mark on one end, unwound, aligned with the indicator mark at the other end and then snapped to produce a visible line after which the chalk line is rewound.
When professional wall boarders are scoring drywall to parallel widths or lengths they will often grasp the measuring tape along its length between their thumb and index finger at a desired measurement. The worker will then employ a utility knife that is pressed against the small metal end of the tape measure. By running the index finger along the straight edge of the drywall while holding the utility knife against the end of the tape measure a parallel scored line is produced. This is a task that takes a great deal of skill as one needs to pull the utility knife and finger holding the tape measure with their varying frictions in unison to produce a straight score line. They also have to be able to hold the utility knife and tape firmly using a small tape end not designed specifically to aid the purpose.
A negative aspect for professional wall boarders using the above method for cutting drywall is that the constant running of their index fingers along an abrasive paper or fibreglass surface often results in cuts or abrasions to the skin. In some cases permanent scaring or injury to the index finger can result after years of using this technique.
In comparison to drywall, for carpenters, the surface of the more abrasive edge on plywood makes using the measuring tape, index finger and pencil in combination for parallel marking more difficult and possibly dangerous. The resulting practice would likely lead to numerous cuts, abrasions and slivers during the course of a working day.
Tape measures are also used as a trammel for laying out circles. A small slot provided on the tape end is used to hook onto the top of a nail or screw at an established center point. With this tape measure design a pencil or other marking instrument can be held against the protruding face of the tape measure housing and the underside of the measuring tape when secured at an indicated measurement. The tape measure housing along with the marking devise can then be pulled towards the worker or pushed away from them to mark the partial or complete circumference of a circle.
There have been many previous attempts to devise a guide for enabling a tape measuring instrument to slide along a straight edge for marking or scoring. Some of these inventions such as Stevens et al. U.S. Pat. No. 5,295,308 and Harris U.S. Pat. No. 5,782,007 have been bulky additions to a tape measure that would inconvenience the user by being obtrusive or a feature constantly needing to be attached and then removed. Others such as Garity U.S. Pat. No. 6,070,338 and Lee et al. U.S. Pat. No. 6,691,425 do not provide a secure locking mechanism to work in a quick responsive ergonomic manner needed for the demands of professionals. Though Garity provides a smooth face it is not noted as being planar and perpendicular to the sides of tape measure housing and the extended tape. A planar smooth face with rounded edges allows the tape measure housing to slide smoothly while also securing the extended tape perpendicular to a straight edged working surface such as plywood, lumber or drywall. If the surface is smooth with any curvature it would make drawing or scoring parallel lines more difficult producing wavy score marks or lines unless the user has accumulated a great deal of skill Both Garity's and Lee et al.'s faces on their tape housing are not designed to ease the reading of measurements while simultaneously providing a functional grasping surface that works in conjunction with a finger controlled pressure locking mechanism.
The many locking mechanisms used for tape measures are not specifically designed to produce the firm, high friction holding capabilities combined with a quick release and ergonomics needed by drywall professionals to work in conjunction with the forces endured with constant, repetitious measuring and parallel marking. Both Hsu U.S. Pat. No. 6,405,451 B1 and Doriguzzi Bozzo, Mario European patent EP 0 932 016 A2 do not provide the significant forces that need to be applied. When the friction surfaces for grasping the tape measure are positioned as a fulcrum it will allow the mechanical advantage of leverage which is greatly increased when pressure is applied to the end of the trigger locks pressure pad distal to the stationary pivot point. A tape measure that combines an improved quick secure locking feature and easy to grasp tape end while also providing a guide that slides and offers a secure ergonomic means to hold the tape's body housing firmly against a materials edge surface will add significant advantages for making quick parallel linear measurements.
The tape ends used for hooking onto building material or stopping a tape that is pushed against material can also be better designed to facilitate the practice of holding onto the end with a scoring or marking instrument while at the same time helping to fulfill other functions. Garity's tape end, U.S. Pat. No. 6,070,338, is off set and angled from the lower portion of the tape end preventing use of the upper portion for pulling accurate measurements. The tape end for Lee et al. U.S. Pat. No. 6,691,425 B1 is also not capable of allowing the upper portion to be used for pulling measurements.